Fans of the danker depths of genre movies will feast on “Free Fire,” a feral exercise in high-energy moviemaking that boils down to an extended shootout in a decrepit warehouse. And I do mean extended: After a modest setup, wild gunplay fills maybe two-thirds of the film’s 90-minute run time.

A comedy and a labor of love, the movie is a takeoff on 1970s action films that’s been stripped of filler to concentrate on pure visceral thrills. The director is Britain’s Ben Wheatley, a cult figure who often works with writer Amy Jump (his wife). Their highly idiosyncratic output includes the 2012 bloody black comedy “Sightseers” and last year’s “High-Rise,” based on a dystopian novel by J.G. Ballard.

Certainly the filmmakers have soaked up the work of Sam Peckinpah, Quentin Tarantino, John Woo and Martin Scorsese (executive producer of “Free Fire”), past masters at depicting over-the-top battles with firearms. Wheatley aims to outdo them all, employing a minimum of plots and a cast of walking, talking action-movie cliches who trade quips and insults between volleys of bullets.

It’s the late 1970s in Boston, and an IRA operative, Chris (Cillian Murphy), with a briefcase full of cash, wants to purchase several dozen high-powered assault weapons. Accompanying Chris are a handful of characters — it’s a terrific cast — played by Brie Larson, Michael Smiley and Sam Riley. Aficionados of wacky ’70s hair and clothing styles will have much to savor.

The sellers are led by Sharlto Copley’s hilariously loutish Vern, wearing what must be the ugliest suit ever made on Savile Row. His team includes Armie Hammer (with beard and turtleneck), a ferocious Jack Reynor and a former Black Panther played by Babou Ceesay.

There’s bad blood between the Reynor and Riley characters. The weaponry Vern brings is not what was requested. And everyone on both sides is armed to the teeth. Guess what follows.

It’s a shootout for the ages, something that might have been choreographed by Chuck Jones (Bugs Bunny, etc.) at his most anarchic — if he had really been into guns. Everyone wants to grab the cash; almost everyone has been wounded (mostly in the limbs), so we see a lot of bleeding people crawling on their bellies and firing at anything that moves. A couple of assassins later join the fray (and who is employing them?) and the film toys with the constant possibility of combatants switching sides. Yes, it’s gunplay, but it’s funny and ghastly at the same time.

To forestall audience burnout, the filmmakers have inserted a few lulls in the action. That helps, as do the comic verbal sallies that accompany the gunfire. Still, after a while we may feel that, OK, we’ve gotten what Wheatley and company are up to, but they are pushing on regardless.

Quibbling aside, “Free Fire” mainly works, as an indulgence in cinematic overkill for moviegoers who realize that sometimes too much is just enough.